Integration of Analog Circuits Inside Digital Blocks

ABSTRACT

A circuit for sensing local operating properties of an integrated circuit is disclosed. The circuit may include one or more sensor circuits configured to sense the local operating properties of the integrated circuit. The sensor circuits may receive a supply voltage with a magnitude in a limited range from a digital power supply that is different from the digital power supply that provides power to functional circuits in the integrated circuit. Level shifters may be coupled to the sensor circuits to shift output signals from the sensor circuits to levels that correspond to the digital power supply that provides power to functional circuits in the integrated circuit. Counters and a shift register may be coupled to the level shifters to receive the shifted output signals, the values of which may be used to determine the local operating properties of the integrated circuit as sensed by the sensor circuits.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/571,228 (now U.S. Pat. No. 11,671,103) filed on Jan. 7, 2022, whichis a continuation of U.S. patent application Ser. No. 16/796,405 (nowU.S. Pat. No. 11,258,447) filed on Feb. 20, 2020. The above applicationsare incorporated herein by reference in their entirety. To the extentthat any incorporate material conflicts with material expressly setforth herein, the expressly set forth material controls.

BACKGROUND Technical Field

Embodiments described herein relate to electronic circuits. Moreparticularly, embodiments described herein relate to electronic circuitsused to sense local voltages and temperatures for an integrated circuit.

Description of the Related Art

As features sizes have decreased, the number of transistors onintegrated circuits (ICs) has correspondingly increased. The increasednumber of transistors per unit area has resulted in a correspondingincrease in thermal output of ICs. Furthermore, the increased number oftransistors per unit area has also corresponded to a decrease in thesupply voltages provided to various functional circuitry on an IC. Thishas in turn led to significant challenges in balancing performance,power consumption, and thermal output of ICs. To this end, many ICsimplement subsystems that monitor various metrics of the IC (e.g.,temperature, voltage, voltage drops) and adjust the performance based onreceived measurements. For example, a control subsystem may reduce aclock frequency, supply voltage, or both, responsive to a temperaturereading that exceeds a predefined threshold. This may help maintainoperation of the IC within specified thermal limits. Such controlsystems may also boost the performance of certain functional circuitswhen measured metrics are well within limits.

IC subsystems used to control performance based on system metricstypically include one or more sensors and at least one control system.In some systems, the sensors may be coupled to receive a power supplyfrom a source separate to other circuitry in the vicinity (e.g., atightly controlled analog power supply). Using an analog power supplyfor the sensors, however, may necessitate complex metrology to integrateand couple the analog power supply to analog elements in a digitalcircuit block. In some systems the use of digital power suppliesassociated with processing units in the digital circuit block to providesupply voltages to the sensors has been contemplated. In such systems,variations in the supply voltages and low supply voltage levels providedto the sensors may reduce the accuracy and performance of the sensors.

SUMMARY

An analog sensor circuit may be integrated inside a digital functionalcircuit block using digital power supplies for the oscillators. Theanalog sensor circuit may include ring oscillators to sense localoperating properties of the digital functional circuit block. In certainembodiments, a substantially fixed or limited range supply voltage(e.g., a SRAM memory power supply) is used for sensor circuits withinthe digital functional circuit block. Using the substantially fixed orlimited range supply voltage, the sensors may provide more accuratemeasurement of local operating properties (e.g., voltage, temperature,or current). Level shifters may be coupled to the sensor circuits toshift levels of the output signals from the sensor circuits to levelsthat correspond to the supply voltage provided to the digital functionalcircuit block.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the methods and apparatus of the embodimentsdescribed in this disclosure will be more fully appreciated by referenceto the following detailed description of presently preferred butnonetheless illustrative embodiments in accordance with the embodimentsdescribed in this disclosure when taken in conjunction with theaccompanying drawings in which:

FIG. 1 depicts a block diagram of an embodiment of an integratedcircuit.

FIG. 2 depicts a diagram illustrating an embodiment of sensor.

FIG. 3 depicts a diagram illustrating an embodiment of a sensor circuitthat implements series-coupled inverters.

FIG. 4 depicts a diagram illustrating an embodiment of a sensor circuitthat implements series-coupled NAND gates.

FIG. 5 is a block diagram illustrating an example of an operationalconcept for an embodiment of a sensor employing two ring oscillators.

FIG. 6 is a flow diagram illustrating a method for determining a voltageand a temperature from a sensor, according to some embodiments.

FIG. 7 is a block diagram of one embodiment of an example system.

Although the embodiments disclosed herein are susceptible to variousmodifications and alternative forms, specific embodiments are shown byway of example in the drawings and are described herein in detail. Itshould be understood, however, that drawings and detailed descriptionthereto are not intended to limit the scope of the claims to theparticular forms disclosed. On the contrary, this application isintended to cover all modifications, equivalents and alternativesfalling within the spirit and scope of the disclosure of the presentapplication as defined by the appended claims.

This disclosure includes references to “one embodiment,” “a particularembodiment,” “some embodiments,” “various embodiments,” or “anembodiment.” The appearances of the phrases “in one embodiment,” “in aparticular embodiment,” “in some embodiments,” “in various embodiments,”or “in an embodiment” do not necessarily refer to the same embodiment.Particular features, structures, or characteristics may be combined inany suitable manner consistent with this disclosure.

Within this disclosure, different entities (which may variously bereferred to as “units,” “circuits,” other components, etc.) may bedescribed or claimed as “configured” to perform one or more tasks oroperations. This formulation—[entity] configured to [perform one or moretasks]—is used herein to refer to structure (i.e., something physical,such as an electronic circuit). More specifically, this formulation isused to indicate that this structure is arranged to perform the one ormore tasks during operation. A structure can be said to be “configuredto” perform some task even if the structure is not currently beingoperated. A “credit distribution circuit configured to distributecredits to a plurality of processor cores” is intended to cover, forexample, an integrated circuit that has circuitry that performs thisfunction during operation, even if the integrated circuit in question isnot currently being used (e.g., a power supply is not connected to it).Thus, an entity described or recited as “configured to” perform sometask refers to something physical, such as a device, circuit, memorystoring program instructions executable to implement the task, etc. Thisphrase is not used herein to refer to something intangible.

The term “configured to” is not intended to mean “configurable to.” Anunprogrammed FPGA, for example, would not be considered to be“configured to” perform some specific function, although it may be“configurable to” perform that function after programming.

Reciting in the appended claims that a structure is “configured to”perform one or more tasks is expressly intended not to invoke 35 U.S.C.§ 112(f) for that claim element. Accordingly, none of the claims in thisapplication as filed are intended to be interpreted as havingmeans-plus-function elements. Should Applicant wish to invoke Section112(f) during prosecution, it will recite claim elements using the“means for” [performing a function] construct.

As used herein, the term “based on” is used to describe one or morefactors that affect a determination. This term does not foreclose thepossibility that additional factors may affect the determination. Thatis, a determination may be solely based on specified factors or based onthe specified factors as well as other, unspecified factors. Considerthe phrase “determine A based on B.” This phrase specifies that B is afactor that is used to determine A or that affects the determination ofA. This phrase does not foreclose that the determination of A may alsobe based on some other factor, such as C. This phrase is also intendedto cover an embodiment in which A is determined based solely on B. Asused herein, the phrase “based on” is synonymous with the phrase “basedat least in part on.”

As used herein, the phrase “in response to” describes one or morefactors that trigger an effect. This phrase does not foreclose thepossibility that additional factors may affect or otherwise trigger theeffect. That is, an effect may be solely in response to those factors,or may be in response to the specified factors as well as other,unspecified factors. Consider the phrase “perform A in response to B.”This phrase specifies that B is a factor that triggers the performanceof A. This phrase does not foreclose that performing A may also be inresponse to some other factor, such as C. This phrase is also intendedto cover an embodiment in which A is performed solely in response to B.

As used herein, the terms “first,” “second,” etc. are used as labels fornouns that they precede, and do not imply any type of ordering (e.g.,spatial, temporal, logical, etc.), unless stated otherwise. For example,in a register file having eight registers, the terms “first register”and “second register” can be used to refer to any two of the eightregisters, and not, for example, just logical registers 0 and 1.

When used in the claims, the term “or” is used as an inclusive or andnot as an exclusive or. For example, the phrase “at least one of x, y,or z” means any one of x, y, and z, as well as any combination thereof.

In the following description, numerous specific details are set forth toprovide a thorough understanding of the disclosed embodiments. Onehaving ordinary skill in the art, however, should recognize that aspectsof disclosed embodiments might be practiced without these specificdetails. In some instances, well-known circuits, structures, signals,computer program instruction, and techniques have not been shown indetail to avoid obscuring the disclosed embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 depicts a block diagram of an embodiment of an integrated circuit(IC). In the embodiment shown, IC 100 includes two functional circuitblocks, processing unit (PU) 130, and PU 140. In various embodiments,other functional circuit blocks may be included, including additionalinstances of PU 130 or PU 140. PU 130 and PU 140 are thus shown here asexemplary functional circuit blocks, but are not intended to limit thescope of this disclosure. Each of PU 130 and 140 may be a generalpurpose processor core, a central processing unit (CPU), a graphicsprocessing unit (GPU), a digital signal processing unit, or virtuallyany other kind of functional unit/circuitry configured to perform aprocessing function. The scope of this disclosure may apply to any ofthese types of functional circuit blocks, as well as others notexplicitly mentioned herein. The number of functional circuit blocksshown here is by way of example as well, as the disclosure is notlimited to any particular number.

In certain embodiments, PU 130 is a general purpose processor coreconfigured to execute the instructions of an instruction set and performgeneral purpose processing operations. Functional circuitry 132 of PU130 may thus include various types of circuitry such as execution unitsof various types (integer, floating point, etc.), register files,schedulers, instruction fetch units, various levels of cache memory, andother circuitry that may be implemented in a processor core.

In certain embodiments, functional circuitry 132 in PU 130 is coupled toreceive first supply voltage Vdd1 from power supply 170. Power supply170 may be a digital power supply such as a processing unit powersupply. It is noted however that multiple power domains, and thusmultiple supply voltages, may be implemented within various embodimentsof PU 130 and functional circuitry 132, as described herein.Furthermore, supply voltages provided to PU 130 and functional circuitry132 may be variable under the control of power management circuitry (notshown). The power management circuitry adjusts the voltages for variousreasons, such as controlling performance levels, thermal output, andpower consumption.

In certain embodiments, PU 140 includes functional circuitry 142, whichmay implement various types of graphics processing circuitry such thatPU 140 is a GPU. This may include graphics processing cores, varioustypes of memory and registers, and so on. In some embodiments,functional circuitry 142 in PU 140 is coupled to receive a second supplyvoltage, Vdd2, from power supply 172. Power supply 172 may be a digitalpower supply such as a processing unit power supply. Power supply 172and second supply voltage Vdd2 may be separate from power supply 170 andfirst supply voltage Vdd1.

In certain embodiments, both PU 130 and PU 140 include a number ofsensors 150. The particular number of sensors 150 shown here is forexample only, and in actual embodiments may be greater, lesser, orequal. Sensors 150 may be configured for sensing one or more operatingproperties of PU 130 or PU 140 (e.g., performance metrics or parametersof the processing units). In certain embodiments, sensors 150 areconfigured to sense operating voltage or operating temperature values(e.g., local operating voltage or operating temperature values for PU130 and/or PU 140). The sensed voltage and temperature values may inturn be used to determine whether or not circuitry implemented therein(e.g., functional circuitry 132 or functional circuitry 142) isoperating within limits and/or is capable of higher performance. In someembodiments, sensors 150 are configured to sense other local operatingvalues such as, but not limited to, current.

In certain embodiments, sensors 150 are coupled to the same power supplyas the functional circuitry in its respective functional circuit blockalong with an additional power supply. For example, as shown in FIG. 1 ,sensors 150 in PU 130 are coupled to power supply 170, which providessupply voltage Vdd1, along with power supply 174, which provides supplyvoltage Vdd3. Correspondingly, sensors 150 in PU 140 are coupled topower supply 172, which provides supply voltage Vdd2, along with powersupply 176, which provides supply voltage Vdd4. Thus, sensors 150 mayreceive multiple supply voltages that are utilized by the sensors asdescribed herein.

As described above, power supply 170 and power supply 172 may beprocessing unit power supplies (e.g., power supplies for CPUs or GPUs).Processing unit power supplies may provide supply voltages that varyfrom power supply to power supply. The variations may be due to, forexample, binning to different values of voltages in different powersupplies or for binning for different operations of the processing unitreceiving the supply voltage. These processing unit power supplies mayalso experience changes in supply voltages due to DVFM (dynamic voltageand frequency management) state changes. These variations in voltage mayreduce the accuracy of operating property sensing using analog circuitelements in sensors 150. Additionally, processing unit power suppliesmay provide low supply voltages that reduce the accuracy of operatingproperty sensing using the analog circuit elements in sensors 150.

In certain embodiments, as shown in FIG. 1 , power supply 174 and powersupply 176 provide a digital power supply voltage with a magnitude ofthe supply voltage being in a limited range. For example, power supply174 and power supply 176 may be fixed digital power supplies, limitedrange digital power supplies, or a combination thereof (e.g., one is afixed digital power supply and the other is a limited range digitalpower supply). A fixed digital power supply may be a power supply thatprovides a supply voltage with a substantially fixed magnitude tosensors 150. The substantially fixed supply voltage may be a voltagethat is fixed at a selected voltage level while there may be someoperational variation in voltage around the fixed selected voltage level(e.g., about ±10%) such that the voltage provided is limited in range. Alimited range digital power supply may be a power supply that provides avoltage with a magnitude that can vary over a small range (e.g., betweenabout ±10% and about ±25%).

In some embodiments, a fixed digital power supply or a limited rangedigital power supply may provide a voltage with a magnitude that remainsabove a minimum voltage magnitude (e.g., the voltage is not a low supplyvoltage as described above). For example, the power supply may provide aminimum voltage magnitude selected to ensure a desired accuracy foroperating property sensing using the analog circuit elements in sensors150. The minimum voltage magnitude selected may vary depending on theoperating parameters of sensors 150 and/or operating properties of IC100, PU 130, and/or PU 140. Examples of minimum voltage magnitudes thatmay be selected include, but are not limited to, 600 millivolts, 750millivolts, and 1000 millivolts

The digital supply voltage with a magnitude in the limited range may beprovided to analog circuit elements in sensors 150, described below, toprovide more accurate sensing of local operating properties. Forexample, power supply 174 and power supply 176 may be digital powersupplies that do not experience binning voltage changes or DVFM voltagechanges that are associated with processing unit power supplies. Powersupply 174 and power supply 176 may be, in some embodiments, powersupplies that provide supply voltages to SRAM memory units (not shown)or other functional circuitry blocks that utilize fixed or limited rangesupply voltages in IC 100. Power supplies for SRAM memory units andother fixed digital supply rails or limited range supply rails may beubiquitous in large digital integrated circuits. Thus, supply voltagesfrom these supplies may be routed to sensors 150 in PU 130 and/or PU 140with small electrical resistances.

In some embodiments, Vdd3 and Vdd4 are the same supply voltage. Forexample, power supply 174 and power supply 176 may provide the samesupply voltage, or power supply 174 and power supply 176 may be a singlepower supply that provides the supply voltage to sensors 150 in both PU130 and PU 140.

FIG. 2 depicts a diagram illustrating an embodiment of sensor 150. Incertain embodiments, sensor 150 includes sensor circuit 152 and sensorcircuit 154. The particular number of sensor circuits in sensors 150may, however, vary. Sensor circuits 152, 154 may include one or moreelements that operate to sense one or more operating properties of afunctional circuit block in which sensor 150 is positioned. For example,sensor circuits 152, 154 may sense operating voltage, operatingtemperature, or operating current of the functional circuit block. Insome embodiments, sensor circuit 152 and sensor circuit 154 sensedifferent operating properties. For example, sensor circuit 152 maysense operating voltage while sensor circuit 154 senses operatingtemperature.

In some embodiments, sensor circuit 152 and sensor circuit 154 includering oscillators. Ring oscillators may be implemented using inverters,NAND gates, other types of inverting circuitry, and various combinationsthereof. FIG. 3 depicts a diagram illustrating an embodiment of sensorcircuit 152 that implements series-coupled inverters. FIG. 4 depicts adiagram illustrating an embodiment of sensor circuit 154 that implementsseries-coupled NAND gates.

In certain embodiments, as shown in FIG. 2 , both sensor circuit 152 andsensor circuit 154 receive the same supply voltage (e.g., Vdd3 forsensor 150 positioned in PU 130 or Vdd4 for sensor 150 positioned in PU140). Sensor circuit 152 and sensor circuit 154 may be provided the samesupply voltage as the sensor circuits are located in close proximity toone another. Though sensor circuit 152 and sensor circuit 154 receivethe same supply voltage, the sensor circuits may have different circuitimplementations (e.g., different ring oscillator implementations) tosense different operating properties. For example, sensor circuit 152may include a ring oscillator that oscillates at a different frequencyfrom a ring oscillator in sensor circuit 154 under identical operatingconditions. Thus, in accordance with discussion below, this may enablethe respective frequencies produced by the ring oscillators in sensorcircuit 152 and sensor circuit 154 to be the basis for solving forvoltage and temperature at sensor 150.

Providing the supply voltage to sensor circuit 152 and sensor circuit154 from a fixed digital power supply or a limited range digital powersupply (e.g., power supply 174 or power supply 176, as described above)may provide advantages in sensing local operating properties with thesensor circuits. For example, with the fixed or limited range supplyvoltage, analog circuit elements, such as ring oscillators, in sensorcircuits 152, 154 are not subject to variations in voltage and/or lowvoltages that can decrease performance and reduce the accuracy of theanalog circuit elements (e.g., if the sensor circuits receive power fromprocessing unit power supplies such as power supply 170 or power supply172). Thus, providing the fixed or limited supply voltage may allow theanalog circuit elements in sensor circuits 152 and 154 to operate withhigh-performance capability and provide improved accuracy in sensinglocal operating properties.

In certain embodiments, sensor circuit 152 is coupled to level shifter156 and sensor circuit 154 is coupled to level shifter 158. Sensorcircuits 152 and 154 may output signals that are responsive to values ofthe local operating properties being sensed by the sensor circuits.Level shifters 156 and 158 may shift the levels of the output signalsreceived from sensor circuits 152 and 154 and provide shifted outputsignals to counters 160 and 162, respectively. The levels of the outputsignal from sensor circuits 152 and 154 may be shifted by level shifters156 and 158 to change the output signal to correspond to supply voltagesfor additional components (e.g., counters 160 and 162) in sensor 150, asdescribed below.

In certain embodiments, counters 160 and 162 are coupled to commonsensor 164. Common sensor 164 may be, for example, a local aging sensor.In some embodiments, common sensor 164, during operation, generates andprovides a local clock signal to each of counters 160 and 162 as well asto register 166. The local clock signal may be used by each of counters160 and 162 as a timer that tracks a run time for allowing the countersto accumulate a count during a measurement. In some embodiments, commonsensor 164 (which may be a free running oscillator in one embodiment)may be less sensitive to voltage and temperature variations than eitherone of sensor circuits 152 and 154. With regard to the particularcircuit topology, common sensor 164 may be, for example, a ringoscillator implemented using inverters, NAND gates, other types ofinverting circuitry, and various combinations thereof. Variousparameters of the transistors used in implementing the circuitry mayalso be varied to achieve the desired sensitivities of common sensor164. In some embodiments, common sensor 164 may be substantiallyindependent of voltage and temperature variations, and more generally,may be less sensitive to these variations than either of the othersensor circuits 152 and 154.

In some embodiments, common sensor 164 is coupled to provide the localclock signal to counters 160 and 162 within sensor 150. Otherembodiments are also contemplated in which a separate clock signal isprovided to each counter. Although one embodiment of a clock circuit insensor 150 is implemented using common sensor 164, it is noted thatother types of circuits capable of generating a clock signal may be usedin other embodiments. Generally speaking, any type of circuit suitablefor generating a periodic signal suitable for use as a clock signal canbe used to implement a local clock circuit in various embodiments ofsensor 150. In some embodiments, common sensor 164 does not provide aclock signal to any circuit external to sensor 150. Furthermore, in someembodiments, none of the circuits in sensor 150 are coupled to receive aclock signal from any source external to the sensor. With respect to itsphysical location, common sensor 164 may be implemented on IC 100 (ormore generally on an IC) in close proximity to the other circuitry ofsensor 150.

In certain embodiments, as shown in FIG. 2 , common sensor 164 mayreceive supply voltage Vdd1 (or Vdd2 depending on the processing unit).Thus, common sensor 164 may receive the supply voltage that correspondsto the supply voltage received in the functional circuitry in theprocessing unit (e.g., functional circuitry 132 in PU 130 or functionalcircuitry 142 in PU 140). In such embodiments, level shifters 156 and158 are used to shift the output signals from sensor circuits 152 and154, respectively, to levels that correspond to Vdd1 for sensors in PU130 (or Vdd2 for sensors in PU 140). Shifting the levels of the outputsignals using level shifters 156 and 158 allows the logic coupled tocommon sensor 164 and Vdd1/Vdd2 (e.g., counters 160 and 162 and register166) to track signals corresponding to the sensed local operatingproperties.

During the taking of a measurement of local operating properties,counters 160 and 162 may receive the shifted output signals from levelshifters 156 and 158, respectively, to track one or more count valuesfor sensor circuits 152 and 154, respectively. The count values incounters 160 and 162 may in turn indicate the frequencies produced byring oscillators (or other sensing elements) in sensor circuits 152 and154, respectively. The respective count values received by counters 160and 162 may be the basis for solving for operating properties (e.g.,voltage and temperature) at sensor 150.

In addition to having different circuit implementations (e.g., differentring oscillator implementations), as described above, sensor circuits152 and 154 may be designed to have different relationships to voltageand temperature with respect to one another. For example, in someembodiments, one of sensor circuit 152 or sensor circuit 154 may bedesigned such that the frequency of its output signal is more sensitiveto variations in voltage than the other one. Similarly, the other one ofsensor circuit 152 or sensor circuit 154 may be designed such that thefrequency of its output signal is more sensitive to variations intemperature than the other one. For the sensor circuit more sensitive tovariations in voltage, the frequency of the output signal of the voltagesensitive sensor circuit (e.g., ring oscillator) may be more stronglydependent on voltage, with the voltage frequency being a function of alarge and linear voltage slope while its relationship to temperature maybe non-linear. Similarly, for the sensor circuit that is more sensitiveto temperature, the frequency of the output signal of the temperaturesensitive sensor circuit (e.g., ring oscillator) may be more stronglydependent on temperature, with the temperature frequency being afunction of a large and linear voltage slope while its relationship tovoltage may be non-linear. Nevertheless, the voltage and temperaturevalues sensed by sensor 150 may be determined as discussed by examplebelow by solving for these quantities based on the respectivefrequencies of the output signals (e.g., the ring oscillator outputsignals).

As shown in FIG. 2 , counters 160 and 162 are each coupled to register166. Register 166 may be, for example, a shift register. Using register166, MCC 102 (shown in FIG. 1 and described below) may input informationinto counters 160 and 162, and may also receive information therefrom.For example, information indicative of a run time for a counter to tracka count value produced by the frequency of a correspondingly coupledsensor circuitry may be input into the counters, from MCC 102, viaregister 166. A start indication may also be input through register 166.From counters 160 and 162, register 166 may receive the count valuesproduced during an actual measurement. In accordance with the embodimentshown in FIG. 1 , these values may be serially shifted through metrologybus 113 to MCC 102 for use in computing the voltage and temperaturevalues. Embodiments in which register 166 is directly coupled to animplementation of MCC 102 are also possible and contemplated.

Returning to FIG. 1 , in certain embodiments, IC 100 includes metrologycontrol circuitry (MCC) 102. MCC 102 may perform various operationsinvolved with operation of sensors 150 in the various functional circuitblocks of IC 100. In the embodiment shown, MCC 102 is coupled to each ofthe sensors 150 via a metrology bus 113. During operation of IC 100,each of the sensors 150 may perform readings of, e.g., a frequency oftheir respective ring oscillator(s), convert the frequency reading intoa digital format, and transmit that information to MCC 102. In certainembodiments, MCC 102 is a serial bus, and information may be shifted onthe bus in operation that is similar to that of a scan chain. However,embodiments utilizing different mechanisms for communications withsensors 150 are possible and contemplated.

MCC 102 may receive the frequency information from each of sensors 150via their correspondingly coupled instances of metrology bus 113. Usingthe frequency information, MCC 102 may determine a voltage andtemperature sensed by each of sensors 150. In some embodiments, MCC 102includes service processor 111 and memory 112. Service processor 111 mayexecute instructions of a software routine to solve for voltage andtemperature values based on frequency information received from each ofthe sensors 150. Embodiments in which dedicated circuitry performs thesetasks in lieu of the execution of software instructions are alsopossible and contemplated. Memory 112 may be used by service processorto store various information, including the frequency informationreceived from the sensors, the determined voltage and temperatureinformation, and intermediate information generated during theperformance of calculations. Memory 112 may also store informationcharacterizing the sensors and the circuitry therein (e.g., the ringoscillators). Memory 112 may be implemented using volatile memory,non-volatile memory, or a combination thereof.

In some embodiments, MCC 102 includes an instance of sensor 120, as wellas a reference sensor 107. Sensor 120 of MCC 102 is coupled to receivesupply voltage Vdd5, (as are service processor 111 and memory 112). Insome embodiments, sensor 120 may be configured in accordance with theother instances of sensors 150 implemented on IC 100. Reference sensor107 may receive its supply voltage from an analog voltage supply, AVdd.In certain embodiments, reference sensor 107 is a high accuracy sensorthat is less susceptible to process, voltage, and temperaturevariations. Temperature readings from reference sensor 107 may be usedas a reference during calibrations, or may be used to determine whenrecalibrations may be necessary.

Example of Ring Oscillators for Voltage and Temperature Sensing

FIG. 5 is a block diagram illustrating an example of an operationalconcept for an embodiment of a sensor employing two ring oscillators. Insome embodiments, each sensor included two ring oscillators that aredesigned to have characteristics different from one another. Moreparticularly, output signal frequencies of each of the ring oscillatorsRO1 and RO2 may have respective relationships to voltage and temperaturethat are different from one another. For example, the frequency of anoutput signal of RO1 may vary more with voltage than with temperature,while the frequency of the output signal of RO2 may vary more withtemperature than with voltage. Furthermore, to provide another example,the frequency of the RO1 output signal may vary more with voltage thanthe frequency of the RO2 output signal, while the frequency of the RO2output signal may vary more with temperature than that of the RO1 outputsignal. Generally speaking, one of the ring oscillators may be moresensitive to voltage variations with respect to the other, while theother ring oscillator may be more sensitive to temperature variations.

The two ring oscillators may be implemented in close proximity to oneanother, and thus may operate under substantially the same voltage andtemperature conditions. However, since their characteristics aredifferent from one another, the two ring oscillators may operate atdifferent frequencies under the same voltage and temperature conditions.This principle may enable the determination of voltage and temperatureat the sensor using frequency readings from each of the ringoscillators.

In the illustrated example, two ring oscillators, RO1 and RO2 arecoupled to Counter 1 and Counter 2, respectively. In taking a reading,each ring oscillator may be allowed to toggle its respectively coupledcounter for a predetermined amount of time. After the predetermined timehas elapsed, the counters may be frozen and their count values providedto indicate frequency.

Each of the ring oscillators RO1 and RO2 may be characterized by apolynomial. More particularly, the frequency output by each ringoscillator may be characterized by a nonlinear function of voltage andtemperature in a form given as shown in Equation 1:

f _(RO)=Σα_(ij) T ^(i) V ^(j)  (1)

Thus, the frequency of RO1 may be characterized as:

f _(RO1)=Σα_(ij) T ^(i) V ^(j)  (2)

while the frequency of RO2 may be characterized as:

f _(RO2)=Σβ_(ij) T ^(i) V ^(j)  (3).

The ‘f’ terms in the above equations may represent frequency, oralternatively, may represent a ratio of a product of the oscillatingfrequency and the number of phases to a reference frequency. Thedetermination of the number of terms in this expression corresponding toa given ring oscillator is dependent on its characteristics. In general,a higher number of nonlinear terms increases the accuracy ofrepresenting the ring oscillator frequency with polynomials.

The output frequencies (or the product mentioned above) may be providedto a non-linear equation solver. Using the polynomials characterizingthe ring oscillators, the simultaneous equations may be solved for bothvoltage and temperature as detected by the sensor. In one embodiment,the non-linear equation solver may be implemented using the serviceprocessor 111 (of FIG. 1 ) and software instructions executed thereby.More generally, the non-linear equation solver may be implemented usinghardware, software, firmware, and any combination thereof. Moreover, itis possible and contemplated in some embodiments that the solving of thenon-linear equations may be performed locally in the correspondingfunctional circuit blocks.

The coefficients in the equations above may be calculated based onactual ring oscillator frequencies for a given set of voltage andtemperature values. Consider a model of a ring oscillator in which thefrequency is defined using a 9-term function a set of 24 data points(voltage, temperature, and output frequency) used to calculate the ringoscillator characteristics. If a higher number of data points is used todetermine coefficients, the resulting function may better characterizethe corresponding ring oscillator. This technique may be referred to assurface fitting of the ring oscillator characteristic, and may usenumerical techniques to map a large set of data points to a polynomial.

As an example, consider a frequency of a ring oscillator as beingdefined by the following expression:

f _(RO)=α₂₂ T ² V ²+α₂₁ T ² V ¹+α₂₀ T ² V ⁰+α₁₂ T ¹ V ²+α₁₁ T ¹ V ¹+α₁₀T ¹ V ⁰+α₀₂ T ⁰ V ²+α₀₁ T ⁰ V ¹+α₀₀ T ⁰ V ⁰  (4)

If measurements of ring oscillator frequency occur at

{(f ₀ ,V ₀ ,T ₀),(f ₁ ,V ₁ ,T ₁), . . . ,(f ₂₃ ,V ₂₃ ,T ₂₃)},

then the following matrices can be formed:

F=[f ₀ f ₁ . . . f ₂₃]  (5)

A=[α ₂₂α₂₁α₂₀α₁₂α₁₁α₁₀α₀₂α₀₁α₀₀]  (6)

X=[X ₀ X ₁ . . . X ₂₃],

in which X _(j) =[T _(j) ² V _(j) ² T _(j) ² V _(j) ¹ T _(j) ² V _(j) ⁰T _(j) ¹ V _(j) ² T _(j) ¹ V _(j) ¹ T _(j) ¹ V _(j) ⁰ T _(j) ⁰ V _(j) ²T _(j) ⁰ V _(j) ¹ T _(j) ⁰ V _(j) ⁰]^(T)  (7).

Accordingly, the frequency F can be defined as F=AX (8). The term A canbe solved for using Least Squares Estimation, computing all thecoefficients in the original surface fit.

This concept can be expanded to two ring oscillators that have adifferent set of characteristics by characterizing each as describedabove. Accordingly, two ring oscillators placed in close proximity toone another, receiving the same supply voltage, and operating atsubstantially the same local temperature, can be characterized in twoexpressions as follows:

$\begin{matrix}\left\{ {\begin{matrix}{f_{{RO}1} = {{\Sigma}_{i,j}\alpha_{ij}T^{i}V^{j}}} \\{f_{{RO}2} = {{\Sigma}_{i,j}\beta_{ij}T^{i}V^{j}}}\end{matrix}.} \right. & (9)\end{matrix}$

The above assumes that the two ring oscillators are characterized withpolynomials having equal lengths, although this is not necessarilyrequired for all instances.

The complexity of solving the simultaneous equations above may bereduced using a piecewise linear (PWL) technique. Using this technique,a two-dimensional nonlinear surface for the output frequency of a ringoscillator can be described using a set of PWL functions. The surface ofoperation over an entire voltage and temperature can be split intomultiple triangular regions over each of which the characteristics of acorresponding can be described using a linear function of voltage andtemperature. Thus, the overall surface may be broken into an integernumber n of PWL regions, described as follows:

$\begin{matrix}{f = \left\{ {\begin{matrix}{{a_{T1}T} + {a_{V1}V} + a_{C1}} & {{for}{region}1} \\{{a_{T2}T} + {a_{V2}V} + a_{C2}} & {{for}{region}2} \\ \vdots & \\{{a_{Tn}T} + {a_{Vn}V} + a_{Cn}} & {{for}{region}n}\end{matrix}.} \right.} & (10)\end{matrix}$

The coefficients for each of the PWL functions can be determined usingthe output frequencies at the three vertices of the triangle describingany given area. For example, for PWL function describing a triangleextending between temperatures T1 and T2 on a first axis and a voltagesV1 and V2 on a second axis, with the frequencies measured at (T₁, V₁),(T₁, V₂), and (T2, V₁) respectively given by f₁, f₂, and f₃ and theindex for the PWL is given as i, the following set of equations can besolved in order to compute the coefficients for the corresponding PWLfunction in that area:

$\begin{matrix}\left\{ {\begin{matrix}{f_{1} = {{a_{Ti}T_{1}} + {a_{Vi}V_{1}} + a_{Ci}}} \\{f_{2} = {{a_{Ti}T_{1}} + {a_{Vi}V_{2}} + a_{Ci}}} \\{f_{3} = {{a_{Ti}T_{2}} + {a_{Vi}V_{1}} + a_{Ci}}}\end{matrix}.} \right. & (11)\end{matrix}$

This can be repeated for every region to determine its PWLcharacteristic, and thus to determine the surface of operation for thering oscillator:

f _(RO)=α₂₂ T ² V ²+α₂₁ T ² V ¹+α₂₀ T ² V ⁰+α₁₂ T ¹ V ²+α₁₁ T ¹ V ¹+α₁₀T ¹ V ⁰+α₀₂ T ⁰ V ²+α₀₁ T ⁰ V ¹+α₀₀ T ⁰ V ⁰

Once both ring oscillators have been characterized with a set of PWLfunction, solving the set of nonlinear equations is reduced to solving aset of PWL equations. The equations to be solved for each PWLcomputation may be generally described as follows:

$\begin{matrix}\left\{ {\begin{matrix}{f_{{RO}1} = {{a_{Ti}T} + {a_{Vi}V} + a_{Ci}}} \\{f_{{RO}2} = {{b_{Ti}T} + {b_{Vi}V} + b_{Ci}}}\end{matrix}.} \right. & (12)\end{matrix}$

Solving these two equations for temperature, T, and voltage, V, resultsin the following:

$\begin{matrix}\left\{ {\begin{matrix}\begin{matrix}\begin{matrix}{T = {\frac{{\left( {f_{RO1} - a_{Ci}} \right)b_{Vi}} - {\left( {f_{RO2} - b_{Ci}} \right)a_{Vi}}}{{a_{Ti}b_{Vi}} - {b_{Ti}a_{Vi}}} =}} \\{{f_{{RO}1}\left( \frac{b_{Vi}}{{a_{Ti}b_{Vi}} - {b_{Ti}a_{Vi}}} \right)} + {f_{{RO}2}\left( \frac{- a_{Vi}}{{a_{Ti}b_{Vi}} - {b_{Ti}a_{Vi}}} \right)} +}\end{matrix} \\\left( \frac{{a_{Vi}b_{Ci}} - {b_{Vi}a_{Ci}}}{{a_{Ti}b_{Vi}} - {b_{Ti}a_{Vi}}} \right)\end{matrix} \\\begin{matrix}\begin{matrix}{V = {{- \frac{{\left( {f_{RO1} - a_{Ci}} \right)b_{Ti}} - {\left( {f_{RO2} - b_{Ci}} \right)a_{Ti}}}{{a_{Ti}b_{Vi}} - {b_{Ti}a_{Vi}}}} =}} \\{{f_{{RO}1}\left( \frac{- b_{Ti}}{{a_{Ti}b_{Vi}} - {b_{Ti}a_{Vi}}} \right)} + {f_{{RO}2}\left( \frac{a_{Ti}}{{a_{Ti}b_{Vi}} - {b_{Ti}a_{Vi}}} \right)} +}\end{matrix} \\\left( {- \frac{{a_{Ti}b_{Ci}} - {b_{Ti}a_{Ci}}}{{a_{Ti}b_{Vi}} - {b_{Ti}a_{Vi}}}} \right)\end{matrix}\end{matrix}.} \right. & {(13),(14)}\end{matrix}$

As previously noted, the calculations discussed herein may be performedin MCC 102, and particularly in service processor 111. This may alloweach sensor 150 to be implemented in a small area and limit its powerconsumption, since it need not perform any conversion of frequency tovoltage and/or temperature. More generally, the features used forfrequency measurement may be implemented within each sensor 150, whilethose features used for PWL computation, calibration against processvariation, again, and accuracy may be implemented within MCC 102.

A surface fit of each ring oscillator (and thus its respective PWLrepresentation) may change over each process corner and may also besubject to local on-die variations. Moreover, the accuracy of a givenring oscillator may be reduced due to effects such as aging.Accordingly, a calibration scheme used for such ring oscillators mayupdate the characteristics of each. These characteristics may be updatedbased on a limited set of accurate measurements from each ringoscillator. If an original (but not accurate) model for a given ringoscillator is

f _(RO_precal)=Σ_(i,j)α_(ij) T ^(i) V ^(j)  (15),

a set of actual measurements may be performed to update the coefficientssuch that a more accurate model of the ring oscillator is as follows:

f _(RO_postcal)=Σ_(i,j)α*_(ij) T ^(i) V ^(j)  (16).

This calibration factors in both the original model and a set ofcalibration points. As the number of points increases, the accuracyincreases correspondingly. Conversely, the efficiency of a calibrationalgorithm may be determined by the accuracy of the post-calibrationmodel based on a smallest number of data points.

In one embodiment, a calibration algorithm in accordance with thedisclosure includes updating the coefficients using a scaled value ofthe error signal at any calibration point. For any of the calibrationpoints, the error signal (e) may be defined as the difference betweenthe actual measurement and the value predicted by the model. That means∀k∈{1, 2, . . . , m}:

e _(k) =f _(k)−Σ_(i,j)α_(ij) T _(k) ^(i) V _(k) ^(i)  (17).

If the coefficients in the original model (α_(ij)) are consolidated in avector given as A₀, a recursive approach may be utilized in which thevector is updated for every single calibration point:

A _(k) =A _(k-1) +e _(k) G  (18).

In one embodiment, the G vector may be determined using the RecursiveLeast Squares (RLS) technique. This may in turn result in a relativelyfast convergence to final desired values based on a limited set ofcalibration data. In using the RLS technique, the G vector isrecursively updated during each step. The RLS technique may utilize analternate characterization of a ring oscillator as follows:

f _(RO) _(precal) =A ₀ U ^(T)  (19),

wherein U is a vector of the (i+1) (j+1) terms, i.e.:

U=[T ^(i) V ^(j) T ^(i-1) V ^(j) . . . T ⁰ V ⁰]  (20).

From this, a diagonal matrix may be formed:

$\begin{matrix}{P_{0} = {\begin{bmatrix}{{var}\left( {U(1)} \right)}^{- 1} & & 0 & & \\0 & & {{var}\left( {U(2)} \right)}^{- 1} & \ldots & 0 \\ & \vdots & & \ddots & \vdots \\ & 0 & & \ldots & {dc}\end{bmatrix}.}} & (21)\end{matrix}$

For any calibration point, the following set of computations may beperformed:

$\begin{matrix}\left\{ {\begin{matrix}{r_{k} = {\lambda + {UP_{k - 1}U^{T}}}} \\{G_{k} = {\frac{1}{r_{k}}P_{k - 1}U^{T}}} \\{\left( {22} \right),} \\{A_{k} = {A_{k - 1} + {e_{k}G_{k}}}} \\{P_{k} = {{\frac{1}{\lambda}P_{k - 1}} - {\frac{1}{\lambda}G_{k}UP_{k - 1}}}}\end{matrix},} \right. & (22)\end{matrix}$

wherein λ is a forgetting factor, and e is the error.

Accordingly, using a recursive least squares algorithm, such as thatdescribed above, the coefficients for a polynomial characterizing a ringoscillator may be updated during a calibration procedure. Suchcalibrations may be performed at various times, such as on a systemstartup, at selected times during the life of the system/IC, responsiveto large variations in reference sensor 107 and sensor 120 in MCC 105,and so forth. As such, voltage and temperature, based on ring oscillatorfrequencies, may be determined with a reasonable level of accuracy overthe life of the system, while enabling the use of simple sensors havinga small area footprint.

Example Method

FIG. 6 is a flow diagram illustrating a method for determining a voltageand a temperature from a sensor, according to some embodiments. Method600 may be implemented using any of the embodiments of a sensor circuitas disclosed herein, in conjunction with any circuitry or othermechanism to solve for voltage and temperature based on respective ringoscillator frequencies.

At 602, in the illustrated embodiment, a first supply voltage from afirst digital power supply is received at a first sensor circuit wherethe first digital power supply provides the first supply voltage at asupply voltage with a magnitude in a limited range and where the firstsensor circuit produces an output signal responsive to a value of afirst local operating property. In some embodiments, the first digitalpower supply provides the first supply voltage at a substantially fixedsupply voltage magnitude. In some embodiments, the first sensor circuitincludes a ring oscillator coupled to the first digital power supplywhere the ring oscillator provides the output signal responsive to thevalue of the first local operating property and where the first counterdetermines the first value based on a frequency of the shifted outputsignal received from the ring oscillator in the first sensor circuit. Insome embodiments, the first supply voltage from the first digital powersupply is received at a second sensor circuit where the second sensorcircuit produces a second output signal responsive to a value of asecond local operating property and where the second local operatingproperty is different from the first local operating property.

At 604, in the illustrated embodiment, a level of the output signal isshifted using a first level shifter coupled to the first sensor circuitwhere the shifted output signal is shifted corresponding to a secondsupply voltage provided by a second digital power supply.

At 606, in the illustrated embodiment, the shifted output signal isreceived at a first counter coupled to the first level shifter.

At 608, in the illustrated embodiment, a first value representing theshifted output signal is determined by the first counter. In someembodiments, a first value from the first counter is received in a shiftregister coupled to the first counter.

In some embodiments, the second supply voltage is received at a ringoscillator coupled to the second digital power supply, a local agingproperty is assessed at the ring oscillator, and an output signalcorresponding to the first counter is provided from the ring oscillatorwhere the output signal corresponds to the local aging property.

Example Computer System

Turning next to FIG. 7 , a block diagram of one embodiment of a system700 is shown. In the illustrated embodiment, the system 700 includes atleast one instance of an integrated circuit 100 coupled to externalmemory 702. The integrated circuit 100 may include a memory controllerthat is coupled to the external memory 702. The integrated circuit 100is coupled to one or more peripherals 704 and the external memory 702. Apower supply 706 is also provided which supplies the supply voltages tothe integrated circuit 100 as well as one or more supply voltages to thememory 702 and/or the peripherals 704. In some embodiments, more thanone instance of the integrated circuit 100 may be included (and morethan one external memory 702 may be included as well).

The peripherals 704 may include any desired circuitry, depending on thetype of system 700. For example, in one embodiment, the system 700 maybe a mobile device (e.g. personal digital assistant (PDA), smart phone,etc.) and the peripherals 704 may include devices for various types ofwireless communication, such as WiFi, Bluetooth, cellular, globalpositioning system, etc. The peripherals 704 may also include additionalstorage, including RAM storage, solid-state storage, or disk storage.The peripherals 704 may include user interface devices such as a displayscreen, including touch display screens or multitouch display screens,keyboard or other input devices, microphones, speakers, etc. In otherembodiments, the system 700 may be any type of computing system (e.g.desktop personal computer, laptop, workstation, tablet, etc.).

The external memory 702 may include any type of memory. For example, theexternal memory 702 may be SRAM, dynamic RAM (DRAM) such as synchronousDRAM (SDRAM), double data rate (DDR, DDR2, DDR3, LPDDR1, LPDDR2, etc.)SDRAM, RAMBUS DRAM, etc. The external memory 702 may include one or morememory modules to which the memory devices are mounted, such as singleinline memory modules (SIMMs), dual inline memory modules (DIMMs), etc.

Numerous variations and modifications will become apparent to thoseskilled in the art once the above disclosure is fully appreciated. It isintended that the following claims be interpreted to embrace all suchvariations and modifications.

Although specific embodiments have been described above, theseembodiments are not intended to limit the scope of the presentdisclosure, even where only a single embodiment is described withrespect to a particular feature. Examples of features provided in thedisclosure are intended to be illustrative rather than restrictiveunless stated otherwise. The above description is intended to cover suchalternatives, modifications, and equivalents as would be apparent to aperson skilled in the art having the benefit of this disclosure.

The scope of the present disclosure includes any feature or combinationof features disclosed herein (either explicitly or implicitly), or anygeneralization thereof, whether or not it mitigates any or all of theproblems addressed herein. Accordingly, new claims may be formulatedduring prosecution of this application (or an application claimingpriority thereto) to any such combination of features. In particular,with reference to the appended claims, features from dependent claimsmay be combined with those of the independent claims and features fromrespective independent claims may be combined in any appropriate mannerand not merely in the specific combinations enumerated in the appendedclaims.

1-20. (canceled)
 21. A circuit, comprising: a first digital power supplythat provides a first supply voltage to first digital functionalcircuitry during use, wherein the first supply voltage is determinedbased on one or more properties of the first digital functionalcircuitry; a second digital power supply, wherein the second digitalpower supply provides a second supply voltage to second digitalfunctional circuitry, the second supply voltage having a magnitude thatremains above a minimum voltage magnitude during use; a sensing circuitconfigured to assess at least one local operating property of the firstdigital functional circuitry by: determining, at the second supplyvoltage, a signal responsive to a value of the at least one localoperating property; shifting the signal to a shifted signalcorresponding to the first supply voltage; and capturing a valuerepresenting the shifted signal.
 22. The circuit of claim 21, whereinthe minimum voltage magnitude for the second supply voltage is above thefirst supply voltage during use.
 23. The circuit of claim 21, whereinthe minimum voltage magnitude for the second supply voltage is selectedto provide a predetermined accuracy for the sensing circuit in assessingthe at least one local operating property.
 24. The circuit of claim 21,wherein the second supply voltage has a substantially fixed magnitude.25. The circuit of claim 21, wherein the sensing circuit includes atleast one sensing element coupled to the second digital power supply,wherein the at least one sensing element is configured to determine thesignal responsive to the value of the at least one local operatingproperty.
 26. The circuit of claim 25, wherein the at least one sensingelement includes a ring oscillator coupled to the second digital powersupply, the ring oscillator being configured to provide the signalresponsive to the value of the at least one local operating property.27. The circuit of claim 21, wherein the first supply voltage is variedbased on dynamic voltage and frequency management of the first digitalfunctional circuitry.
 28. The circuit of claim 21, wherein the sensingcircuit is configured to accumulate a plurality of values representing aplurality of shifted signals over a period of time for a measurement ofthe at least one local operating property.
 29. The circuit of claim 21,wherein the sensing circuit is configured to assess at least oneadditional local operating property of the first digital functionalcircuitry by: determining, at the second supply voltage, an additionalsignal responsive to a value of the at least one additional localoperating property, wherein the at least one additional local operatingproperty is different from the at least one local operating property;shifting the additional signal to an additional shifted signalcorresponding to the first supply voltage; and capturing an additionalvalue representing the additional shifted signal.
 30. The circuit ofclaim 29, wherein the at least one local operating property is a voltageof the first digital functional circuitry, and wherein the at least oneadditional local operation property is a temperature of the firstdigital functional circuitry.
 31. A circuit, comprising: a first digitalpower supply that provides a first supply voltage to first digitalfunctional circuitry during use, wherein the first supply voltage isdetermined based on one or more properties of the first digitalfunctional circuitry; a second digital power supply, wherein the seconddigital power supply provides a second supply voltage to second digitalfunctional circuitry, the second supply voltage having a magnitude in alimited range that is not varied during use based on one or moreoperating properties of the second digital functional circuitry; asensing circuit configured to assess at least one local operatingproperty of the first digital functional circuitry by: determining, atthe second supply voltage, a signal responsive to a value of the atleast one local operating property; shifting the signal to a shiftedsignal corresponding to the first supply voltage; and capturing a valuerepresenting the shifted signal.
 32. The circuit of claim 31, whereinthe second supply voltage has a substantially fixed magnitude.
 33. Thecircuit of claim 31, wherein the sensing circuit includes at least onering oscillator coupled to the second digital power supply, wherein theat least one ring oscillator is configured to determine the signalresponsive to the value of the at least one local operating property.34. The circuit of claim 31, wherein the first supply voltage is variedbased on dynamic voltage and frequency management of the first digitalfunctional circuitry.
 35. The circuit of claim 31, wherein the sensingcircuit is configured to accumulate a plurality of values representing aplurality of shifted signals over a period of time for a measurement ofthe at least one local operating property.
 36. The circuit of claim 31,wherein the sensing circuit is configured to assess at least oneadditional local operating property of the first digital functionalcircuitry by: determining, at the second supply voltage, an additionalsignal responsive to a value of the at least one additional localoperating property, wherein the at least one additional local operatingproperty is different from the at least one local operating property;shifting the additional signal to an additional shifted signalcorresponding to the first supply voltage; and capturing an additionalvalue representing the additional shifted signal.
 37. A system,comprising: a plurality of integrated circuits, wherein one or more ofthe integrated circuits includes: a plurality of functional circuitblocks each including functional circuitry; a first digital power supplythat provides a first supply voltage during use; a second digital powersupply, wherein the second digital power supply provides a second supplyvoltage to second digital functional circuitry, the second supplyvoltage having a magnitude that remains above a minimum voltagemagnitude during use; and a plurality of sensors, wherein each of theplurality of functional circuit blocks includes at least one of theplurality of sensors implemented therein, and wherein at least one ofthe plurality of sensors is configured to: determine, at the secondsupply voltage, a signal responsive to a value of at least one localoperating property; shift the signal to a shifted signal correspondingto the first supply voltage; and capture a value representing theshifted signal.
 38. The integrated circuit of claim 37, wherein theminimum voltage magnitude for the second supply voltage is above thefirst supply voltage during use.
 39. The integrated circuit of claim 37,wherein the at least one of the plurality of sensors is furtherconfigured to: determine, at the second supply voltage, an additionalsignal responsive to a value of at least one additional local operatingproperty, wherein the at least one additional local operating propertyis different from the at least one local operating property; shift theadditional signal to an additional shifted signal corresponding to thefirst supply voltage; and capture an additional value representing theadditional shifted signal.
 40. The integrated circuit of claim 39,wherein the at least one local operating property is an operatingvoltage of at least one functional circuit block, and wherein the atleast one additional local operating property is a temperature of the atleast one functional circuit block.